The term “dissolved solids” refers generally to any minerals, salts, metals, cations or anions that are dissolved in a water sample. Dissolved solids include many of the substances that impair water color, odor, taste, or overall water quality. Many industries, and the food service industry in particular, require that the water used be held to stringent standards such that the color, odor, or taste of the water does not have any adverse effect on the end product. Many available water supplies exceed the EPA's recommended maximum total dissolved solids (TDS) level of 500 parts per million (ppm); therefore treatment and monitoring of water sources for TDS levels is important to maintaining a desired water quality for particular industrial or commercial activities.
The monitoring of TDS levels from a water source can effectively help in determining the appropriate types of water processing and/or treatment that must be applied to the water to obtain a water output within a desired range of TDS levels.
Many types of water purification systems may be used to reduce the level of TDS from a water source. These water purification systems include distillation and deionization systems; however, the most thorough method of large-scale water purification is reverse osmosis filtering, wherein the water is forced under pressure through a semi-permeable membrane that allows water to pass through while removing most TDS contaminants.
The measurement of TDS in a water supply is not only important for determining the proper type of water purification system that should be used to treat used to treat the water, but is also important for the continual monitoring of the water from the purification system to ensure that the desired TDS output levels are being achieved. A detected rise in the measured TDS level may be indicative of increased contaminants in the water supply source, and a new or modified water purification system may be needed. Alternatively, the detected rise in measured TDS may be indicative of reduced filtering capacity, thus indicating that it is time to replace the filter. Specifically in monitoring the function of a reverse osmosis system, a rise in TDS levels may indicate a compromised membrane that may need replacement.
Devices and methods currently exist for monitoring the TDS in a water source. Many of these devices are based on the principle that the conductivity of the water being tested increases as the TDS in the water increases. Therefore, the TDS may be measured by inserting a pair of electrodes into the water to be tested and measuring the conductivity between the two electrodes experienced by a current passed between them. These TDS meters have been developed both as stationary in line systems that are inserted into the water purification system just prior to the water output, or may exist as portable, handheld device.
The handheld devices are popular for use by technicians in conducting field tests of water sources, either in preparation for recommending a new water purification system for a customer or as part of regular maintenance and water purification system check-up.
However, handheld TDS meters are not practical for casual use by a customer or a layman. This is due to the fact that handheld TDS meters are prohibitively expensive for consumers that may only use the handheld TDS meter once or twice a year, or for potential consumers interested in obtaining more information about their specific water filtering needs. In addition to the cost, some TDS meters are complex to operate and/or install such as to make it difficult for customers or layman to obtain accurate results. Additionally, many TDS meters display the measured TDS value in numeric form indicating the parts per million (ppm) of TDS. The lay consumer is not trained to interpret this measured value of TDS in ppms to understand TDS in ppms to understand the quality of the water source. The TDS meters that are available are intended for regular use and testing many water samples over time. Therefore it is not economically practical for a consumer to purchase one of the currently available TDS meters for annual or semi-annual water system testing. Furthermore, the expense of current handheld TDS meters makes it difficult for the wide spread dissemination in use of the TDS meters by all of the clients of a provider of water treatment products and services.
The TDS in a water supply may be alternatively monitored with the use of paper test strips that change color based upon the TDS level of the water in which they are placed. However, these test strips are typically difficult to properly use and interpret and do not identify the TDS level with a sufficient specificity in order to properly assess water purification needs, or to monitor the on-going function of an existing water purification system.
Therefore, it is desirable in the field of water purification services and monitoring for a disposable electronic TDS meter. Such a meter may be widely disseminated amongst current or potential water purification system and services customers for reliable monitoring of water supply TDS levels by customers that may not be trained in the specifics of water TDS monitoring.